Patent GB-1255841-A (GB)
Title: Character memory
IPC: G09G1/08
Filed: 1969-01-14
Abstract: 1,255,841. Cathode-ray tube displays. HARRIS-INTERTYPE CORP. 14 Jan., 1969 [4 March, 1968], No. 2251/69. Heading H4T. [Also in Division G4] Digital information representative of each of a plurality of Alpha-Numeric characters to be displayed on a cathode ray tube by controlling the beam in accordance with such information is recorded on a rotating Storage member in a repeated sequence which is divided into a plurality of sections including, in addition to character information, digital data indicating the beginning and end of each section and digital data representative of the X, Y starting coordinates. This arrangement allows a character to be displayed under the control of information derived from any sequence of sections so that the " recovery " time is reduced over systems which must " wait " until the beginning of the stored character information reaches the position of the reading head. Optical or magnetic storage means may be employed.  The described embodiment utilizes an optical storage member comprising an optically transparent disc 11 (Fig. 1) on which digital data representative of each character is stored as optical marks in at least one track such as 40 (Fig. 2). As shown, the data appertaining to one character is repeated four times in quadrants A, B, C and D and the data in each quadrant is divided into three sections I, II, III each of which includes further data indicative of the beginning and end of the section and data indicative of the X, Y co-ordinates of the beginning of that portion of the character represented by the data relative to the remainder of the character. The disc carries a plurality of such tracks appertaining to different characters, symbols &c. and in addition, includes timing tracks 35, 36 for overall control of the system. As the disc rotates the data on each track is sensed by a light source 12 and fibre optic assembly 13 connected to respective photoelectric tubes over individual optical fibres 14. The particular character to be displayed is selected by means of a tape 21 and the data signals appertaining thereto are supplied to a character generator 20 which supplies signals to the display tube 30 to produce the character in a position determined by signals derived from the tape via a control circuit 25. The characters are produced either by deflecting the beam between successive X, Y co-ordinates at each of which a bright-up pulse is supplied to the beam so that the character is displayed as a series of bright dots or, bright up of selected points on a line scanned raster may be employed. Fig. 4 shows an example of the latter method of operation where each section is specified by a common Y co-ordinate (the same for all characters) and by the start co-ordinates X1, X2, X3 of the respective sections I, II and III and Figs. 7a, 7b and 7c show the manner in which the character is reproduced when the order of sensing of the sections is III, I, II, the black dots indicating the section currently being produced and the broken dots the sections previously reproduced. When the character is produced by deflecting the beam between successive X, Y co-ordinates the start co-ordinates of each section must include the Y co-ordinate in addition to the X co-ordinate (Figs. 5, 6, 8a, 8b, 8c, not shown).